Small Heat shock proteins (sHsps) are molecular chaperones that are virtually ubiquitous in all known types of organisms and preserve denaturing proteins from irreversible aggregation due to different stressors, especially heat stress. However, even though their obviously vital role, comparatively little is known about sHsps.
Mammalian Hsp27 (HspB1) has not only shown an importance in the human heat shock reaction, but recent studies have also linked its activity to anti-apoptotic effects as well as tumorigenesis and cancer progression, including metastasis spreading effects. Mutations of Hsp27 were also directly associated with diseases of the peripheral nervous system including the most common inherited motor and sensory neuropathy, the Charcot-Marie-Tooth disease. These findings make human Hsp27 one of the possibly major therapeutic targets of the future and make the essentiality of a more extensive research on Hsp27’s properties obvious.
In this work the focus was set on the chaperone activity (i.e. heat stress response) of human Hsp27 and a possible correlation to changes in the surrounding pH conditions. Hsp27 was expressed and purified and subsequently comparison in oligomer formation as well as aggregation suppression was analysed in an acidic and an alkaline environment in vitro (pH 6.3 and 7.5 respectively).
Chaperone activity assays with the well established model chaperone substrate Citrate Synthase as well as analytical size exclusion chromatography profiles show no significant differences in chaperone activity. Neither molecular mass and quantity of appearance of the protein nor aggregation suppression rates indicate any differences of the chaperone activity of human Hsp27 under varying pH conditions.